Structural Design of Sandwich Towers for Wind Energy Converters

A new kind of tower construction, called a sandwich tower, has been developed for wind energy converters. The tower consists of two steel shells, which are bonded together with a core material. Unlike a standard steel tower, the plate thickness is split into an inner and outer steel face. The core between the faces increases the stability of the shells. It works together like a sandwich shell. Different composite shell theories have been used to estimate the stability of such double-skin shell constructions. A model-scale test series has been carried out to analyse the influence of different core materials. The test specimens are loaded by uniform axial force to observe the shell buckling. The experimental results are compared to numerical simulations including measured geometrical imperfections. Within a numerical pre-design, the use of high-strength steels for the inner and outer faces is also considered to compare the various types of tower configurations. The goal is to find the best combination of steel faces with a core material in the ultimate limit state.

By Peter Schaumann and Christian Keindorf, ForWind, Germany